Flow rate vs tank size rating?

[mkatts]

So I am shopping planning and saving for a big tank. 75 to 150g so far is some that I liked. I started looking at filter options and am getting confused. Understanding the need to turn the water over 4 times an hour, 150 gallon tank would need a flow rate of 600gph. Correct?
So I am finding cannister filters that say they are are good for up to 200 gallon tanks but have a flow rate of 365gph.
Soo is that a marketing ploy and I should focus only on flow rate on a filter?
I like the fluvial fx6. 900gph and and a 10.8 head height. This 150 I'm looking at is 48in wide, 24in deep and I think 36in tall. Not postive on how tall. Was focused at the time on width and and depth for fitting into the planned space. I don't want want a hob filter. Want to minimize the visible hardware all around.
Any other make/model of canister filters. At $340 for the fx6 I want to be sure I'm not over buying.
Thanks all!

[mkatts]

anyone?

[BBradbury]

Hello mk...

I'm not a fan of canister filters. Too expensive unless you plan to keep and breed expensive fish. Then I guess you might need high end filters. The hang on the back type are a third the cost and do essentially the same job.

I use Hagen filters and for a 75 G a couple of HC 70s placed at opposite ends of the tank would be sufficient. If you decide on the 150 G, then go with two HC 110s. A 75 G is a good sized tank and would give most fish more than enough room and allow you to keep the tank water work at a reasonable level.

I keep larger tanks and change a lot of tank water every two weeks. 150 Gs would be quite a bit of work to change the tank water and I don't believe the 150 is twice as nice as the 75, just twice the work to maintain.

B

[mkatts]

Thanks!
My main question was more so around which number to focus on for any filter type.
Flow rate or tank size?

To your comment, the quantity of the water doesn't concern me too much. My goal is to have a tank that at eye level i can see at least some of the fish. That is the only reason I considered this particular tank. With it's included stand it stands about 5ft so still a bit short. I have considered building an additional pedestal for it as well.
The issue I have wit the HOB's is that they are up on the tank. What I am planning, I want to the tank as close to the wall as i can and want minimal "bulk" on top. I thought with the cannister hidden underneith, all I would have to the inlet and outlet tubes and the heater/s. Which will be behind a false back drop. The back drop is another reason this 150G appealed to me. It's 24" deep, so I have plenty of room to make some caves and what not.

[mattcham]

The advertised flow rates on filters are when used with no media. With media it can go down 70% especially if your media are clogged with debris. Water polishers (low micron filter floss media) clog especially fast and impede flow.

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[mkatts]

Understand. But which number should a shop for? Flow rate or rated tank capacity?

[mattcham]

Flow rate for sure. Notice that canister filters in general have relatively low flow rates for the price. The Aquaclear 110 is 500 gallons per hour for $85 while Fluval FX6 canister is also 500 gph for $300. Maybe better for water quality to have three Aquaclear 110 than just one FX6. Also if filter breaks its good to have redundant filter. If money is no object buy two FX6.

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[BillD]

Don't get caught up in flow numbers and turnover rates; they are more for discussion on forums. On forums you will be told by many that you need a 10x turnover rate. That is, a 100 gal tank would need to have a flow rate of 1000 gals per hour. However, you will find for the most part that filters will have a gallon rating, and the flow rate will be nowhere near 10 times. Why is that? The reason is that everyone on a forum knows more about filtration than the manufacturers. (Really?)
Bottom line is that if the filter is capable of 0 ammonia and 0 nitrite, it is sufficient in capacity. More flow might do some things, such as remove more debris, but won't reduce those numbers. If you look at the Hamburg/mattenfilter, the desired flow rate is 1 to 1.5X per hour. It works really well, but it doesn't suck up stuff and hide it in a can.

[mkatts]

Thank you everyone for your input. Looks like there is some debate on this topic. I don't want to start any arguments though. But I will take everyone's input. I think what I am going to look at is maybe two smaller rated canisters that combined will provide enough turnover. That gives me a level of redundancy as well should I have a failure. Not N+1, but half capacity is better than none at all in an emergency.
I found a Sunsun that is rated for 150 gallons and 525GPH for $92. Two of them would put me way over on both rated gallons and GPH, plus give me redundancy.

[mattcham]

I agree with BillD, despite my reliance on flow rate. Other things to consider are the biological filter volume/capacity. The FX6 biological filter capacity for example is 1.5 gallons, which is about the same as four AquaClear 110 filters.

In addition to SunSun, look into Penn Plax cascade also for around the same budget.

[mkatts]

Cool. thanks!